1. Lecture 31: Mid-Term Review
ENGI 1313 Mechanics I
Lecture 31: Mid-Term Review

2. Overall Mid-Term Results
Class Statistics (259)
Average
67%
Standard deviation
17%
Standard deviation between sections 3%
Solution Posted

3. Term A/B Exam (Mon. Oct 22) Results are not Back Student Numbers

4. No Record of Mid-Term Exam
Contact Me Immediately to Resolve
Student Numbers

5. Problem 1
Determine the components of the F force acting along the u and v axes.
Given:
1 = 70
2 = 45
3 = 60
F = 250N

6. Problem 1 (cont.) Problem Characteristics Solution Method
Force vectors
No right rectangular coordinate system
Forces on specified axes
Solution Method
Parallelogram or triangle construction
Law of sines

7. Problem 1 (cont.)
Force Triangle  Fv
F = 250 N
1 = 70
2 = 45 Fu

8. Problem 2
The three cables are used to support the lamp of weight W. Determine the force developed in each cable for equilibrium.
Given:
a = 4 m
b = 4 m
c = 2 m
W = 600 N
4 m
2 m
4 m
W = 600 N

9. Problem 2 (cont.) Problem Characteristics Solution Method
Particle Equilibrium
Scalar or vector approach
Solution Method
Summation of Forces
4 m
2 m
4 m
W = 600 N

10. Problem 2 (cont.) FBD and Unit Vectors FAD 4 m 2 m 4 m FAB FAC
W = 600 N

11. Problem 2 (cont.) Equilibrium Equation Three Equations FAD 4 m 2 m 4 m
FAB
FAC
W = 600 N

12. Problem 3
Force F is applied to the handle of the wrench. Determine the angle  between the tail of the force F and the handle AB.
Given:
a = 0.30 m
b = 0.50 m
F = 80 N
1 = 30
2 = 45
F = 80N  1 2
0.3 m
0.5 m

13. Problem 3 (cont.) Problem Characteristics Solution Method
Vector projection
Solution Method
Dot product
F = 80N  1 2
0.3 m
0.5 m

14. Problem 3 (cont.) Unit Vectors Dot Product F = 80N  30 0.3 m 0.5 m
45
0.3 m
0.5 m

15. Problem 4
The hood of the automobile is supported by the strut AB, which exerts a force F on the hood. Determine the moment of this force about the hinged axis y.
Given:
a = 0.60 m
b = 1.50 m
c = 0.25 m
d = 1.00 m
F = 100 N

16. Problem 4 (cont.) Problem Characteristics Solution Method
Moment about a specified axis
Solution Method
Triple scalar product

17. Problem 4 (cont.)
Unit Vector
Moment about Y-axis